This invention relates generally to power supply and power regulation applications, and more specifically to DC-DC power converters using synchronous power rectification.
DC-DC converters or switching regulators are widely established as an efficient means to convert one DC voltage to another desired DC voltage in electronic applications that require a stable power supply potential. In general, a DC-DC power converter is coupled to an input power source with a voltage level either lower than or higher than the voltage level required by an electronic device. Switching regulators indirectly regulate an average DC output voltage to a device or application by switching energy on and off in an inductor. By comparing the output voltage to a reference, the inductor current can be controlled to provide a desired output voltage.
Boost converters are implemented in applications requiring a higher operating voltage than is supplied by the input power source. Conversely, buck converters are utilized in applications requiring a lower operating voltage than is supplied by the input power source. A rectification circuit element such as a Schottky diode is commonly employed within the converter to enable uni-directional energy flow from the input power source to the electronic device or application.
Synchronous buck converters are a specific type of switching regulator that provide improved power efficiency over traditional converters by replacing the Schottky diode with a power switching device such as a power MOSFET device. A high-side switch (control switch) selectively couples the inductor to a positive input power supply, while a low-side switch (synchronous switch) selectively couples the inductor to ground. The high-side and low-side switches typically are controlled using a pulse width modulation (PWM) control circuit, although other control techniques such as ripple regulators and pulse frequency modulation (PFM) are known as well.
With continued advances in electronic devices and applications, power designers are driven to improve and optimize power consumption and efficiency. Although synchronous buck converters provide improved power efficiency compared traditional buck converters, power loss problems still exist. For example, significant power losses occur due to body diode conduction and reverse recovery in the low-side power MOSFET. Such losses result from a delay in switching between the high-side and low-side switches, which is necessary to prevent simultaneous conduction in both switches.
Accordingly, a needs exists for dc power regulation systems and methods for optimally controlling delay time when switching from a high-side switch to a low-side switch.